Historical TLDs

A .nato was added in the late 1980s by the NIC for the use of NATO, who felt that none of the then existing TLDs adequately reflected their status as an international organization. Soon after this addition, however, the NIC created the .int TLD for the use of international organizations, and persuaded NATO to use nato.int instead. However, the nato TLD, although no longer used, was not deleted until July 1996.

Debated TLDs

About the time that ICANN discussed and finally introduced .aero, .biz, .coop, .info, .museum, .name, and .pro TLDs, site owners and USENET users argued that a similar TLD should be made available for adult and pornographic websites to settle the dispute of obscene content on the internet and the responsibility of service providers under the questionable Communications Decency Act of 1996. Several options were proposed including .xxx, .sex and .adult, but so far ICANN has chosen not to create any.

An older proposal consisted of seven new gTLDs .arts, .firm, .info, .nom, .rec, .shop, and .web. Later .biz, .info, .museum, and .name covered most of these old proposals.

On 26 June2008, ICANN approved the relaxation of the rules for the introduction of new TLDs. The new rules will allow any public or private entity from anywhere in the world to register any string of letters as a gTLD. Observers believed that the new rule could result in hundreds of new gTLDs registered this year.

Pseudo-domains

In the past the Internet was just one of many wide-area computer networks. Computers not connected to the Internet, but connected to another network such as BITNET, CSNET or UUCP, could generally exchange e-mail with the Internet via e-mail gateways. When used on the Internet, addresses on these networks were often placed under pseudo-domains such as .bitnet, .oz, .csnet, and .uucp; however these pseudo-domains implemented in mail server configurations such as sendmail.cf and were not real top-level domains and did not exist in DNS.

Most of these networks have long since ceased to exist, and although UUCP still gets significant use in parts of the world where Internet infrastructure has not yet become well-established, it subsequently transitioned to using Internet domain names, so pseudo-domains now largely survive as historical relics. One notable exception is the 2007 emergence of SWIFTNet Mail, which uses the .swift pseudo-domain.

.local deserves special mention as it is required by the Zeroconf protocol. It is also used by many organizations internally, which will become a problem for those users as Zeroconf becomes more popular. Both .site and .internal have been suggested for private usage, but no consensus has yet emerged.

TLDs in alternative roots

ICANN's slow progress in creating new gTLDs, and the high registration costs associated with TLDs, contributed to the creation of alternate root servers with their own sets of TLDs. At times, browser plugins have been developed to allow access to some set of "alternative" domain names even when the normal DNS roots are otherwise used.

The anonymity network Tor has a pseudo-domain .onion, which can only be reached with a Tor client because it uses the Tor-protocol (onion routing) to reach the hidden service in order to protect the anonymity of the domain.